Hysteresis and thermodynamic properties of water sorption in ‘Malagueta’ pepper seeds

Hellismar W Da Silva,Renato S Rodovalho,Isneider L Silva

doi:10.1590/1807-1929/agriambi.v22n9p658-663

Abstract

ABSTRACT The objective of this study was to determine hysteresis, enthalpy, entropy, enthalpy-entropy compensation theory and Gibbs free energy for water adsorption and desorption in ‘Malagueta’ pepper seeds. Hygroscopic equilibrium moisture contents were determined by the static gravimetric method, with water activity in the range from 0.29 to 0.90 and temperatures of 30, 40 and 50 °C. The hysteresis of the ‘Malagueta’ pepper seeds reduces with the increase of temperature. Enthalpy, entropy and Gibbs free energy of adsorption and desorption increase with the reduction of the moisture content of the seeds. The enthalpy-entropy compensation theory is valid for the sorption processes. The sorption of water between seeds and the surrounding air is a non-spontaneous process.

Highlights

Peppers and bell peppers of the genus Capsicum are traditionally used in Brazilian cuisine
This study aimed to determine hysteresis, enthalpy, entropy, enthalpy-entropy compensation theory and Gibbs free energy related to water adsorption and desorption in ‘Malagueta’ pepper seeds
The hysteresis of the pepper seeds decreased with the increase in temperature (Figure 1D), showing a similar behavior to those observed for ‘Bode’ pepper (Capsicum chinense L.) (Rodovalho et al, 2015), millet (Aviara et al, 2016) and castor beans (Goneli et al, 2016b)

Summary

Introduction

Peppers and bell peppers of the genus Capsicum are traditionally used in Brazilian cuisine. It is estimated that in 2016 the world production of fresh peppers and bell peppers has reached 51.9 million tons (FAOSTAT, 2018), which can be justified by the use of production technologies such as highquality seeds. Due to the hygroscopic behavior, the moisture content of seeds is influenced by the temperature and relative humidity of the air (Silva & Rodovalho, 2016). This behavior directly interferes with the biological activity and longevity of these seeds (Silva et al, 2015b). The hygroscopicity of a product is defined as its ability to release or absorb water from the environment, phenomena known as water desorption and adsorption (Corrêa et al, 2014). The difference between adsorption and desorption isotherms (hysteresis) allows the evaluation of chemical and microbiological deterioration and stability of the product during storage (Goneli et al, 2016b)

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